Gas turbine combustor having tangential air inlets for primary and secondary air



NATHAN GAS TURBINE COMBUSTOR HAVING TANGENTIAL AIR May 19, 1953 M.

INLETS FOR PRIMARY AND SECONDARY AIR 3 Sheets-Sheet 1 Filed Nov. 7, 1945VIIIE M. L. NATHAN 2,638,745 GAS TURBINE COMBUSTOR HAVING TANG TIAL AIRINL S FOR PRIMARY AND SECOND AIR Filed Nov. 7, 1945 3 Sheets-Sheet 2 May19, 1953 M. L. NATHAN GAS TURBINE COMBUSTOR HAVING TANGENTIAL AIR May19, 1953 INLETS FOR PRIMARY AND SECONDARY AIR 3 Sheets-Sheet 5 FiledNov. 7, 1945 Patented May 19, 1953 GAS "TURBINE JCOMBUSTOR HAVING :TA'N-.GENTIAL :Am :mm'rs iron PRIMARY: AND SECONDARY Am Matthew"Lewis Nathan,Gotlalming,-England, assigli'or to Power Jets (Research '& Development)Llmitedflzondon, England SectionLPubl-icLaw 690, Augusit 8, 15146 Patentexpires April 1, 1963.

t 4 Claims. (.01. ,co ,-39.-65)

This invention relates to combustion arrangements-for burning flu-idfuel in an airastream. It -is applicable more particularly (though notexclusively) to l an arrangement for combustion tube as "being of two:or even "threewkintls; ":primary air .is that :proportion of the wholethroughput"- Which is required to sustain :combus diluent, and "tertiaryair if vprovided 101', is mainly air which is a diluent. Diluentlairzis, of

-course,: air overxand above that which is required iorcomhustion butwhich. is required to be heated for the operation OFT/he! power unitizorother pur- Thepresent invention comprises ine ifect aform oi fiame tubewhich Jhassshown' itself 1 in ;.:pra.ctise to meet actual requirements,:has 1a 1 reasonably a long life, is simpleto'make' andis light. inweight. -Aiunctional objectof theinventioni isxtoisohtain a correct 1balance "between primary, secondary and tertiary air: flow and to socontro-lcthesethat the distribution of the flow isravourable forcom-"bu'stion inparticular it appears from' experiment thatthe arrangementpermits the inject-edfuel in vaporizefthorough'ly' without beingchilled.

-=Accorcling to the inventioma flame tnbeforuse with i one end open foremission .of combustion products and the other end closed except forminor; perforations, provision beingxmadeifor. the

introduction \of fuel into'the-tube in the region of of.1i i z -f dfuelin apcompressorand the closedeendtthevwall of the:tubein-this regiongas-turbine power unit. The particular usewof (within whichiprimarycombus on take P c the invention at present envisaged is as aflameham'l'lg openin s fi ed wlth mea s which ditube-in an aircraftpropulsion. power unit comrect primaryairinto the tube -.inattangen-tial prising an air compressor; a plurality of combus-'ensepwhi'ls o e op n s. arez tion chambers supplied thereby, and a gasturtube 'wallzfurther towardsithe openendlikewise bine drivingthecompressor by power derived associatedwith-airdirecting:means-forsecondary from the combustion products one continuousair to enter theatubezin-a: tangential sense. :The basis. In such unitsit maybe assumed that each fuel is 2 preferably liquidiuehinjectedintthemecombustion chamber comprises: a cylindrical gionnoftheclosedend; theairdirectingmeans outer chamber t rw ia e ntersat one endare mainly external totheborezof the tube and and aninneriiametubeofless diameter, into their purposeistocausethe.enteringsairtoeswirl which the air passesirom the=annular spaceibeinthe bore in' vortex manner. The openings and tween the chamber andflametube; the latter associated air directing means inanyone axiallydisehargesfro-m one endpsubstantial'ly axially; :definedregion of.theitube are; provided asaring l'he achievement o'f efficientcombustion over 2 or circumferentia1:series and evenly .spaced in a widerange of mixture strengths and. in various the circumferential .-sense...Beside the openings operating conditions is in itselfadifficult!techniwhich have air directing means other openings cal problem whenlimitations; o-favolume; highxair are preferably providedwhich; are.plain and these velocities, and-the-necessity'for:avoidingwcarbon "aredistributed z'mainly towards .the open-lend of "deposition andexcessivelocal heating-vareutaken the tube. [Fl-1e airvdirectingmeans in oneaxially into account. Itistalsotdcemedito'he desirable located; region"may beroppositelyhanded in rotathat stratification of. gases in theoutlet (i.-I8.-Wid6 tional sense'to those of an adjacent reg-1e11,.i.-,e. variations of temperature across; a' section ref-the one furtherup'or down stream. .The air'directfiow) is to'tbe'minimised. ing meansmay-comprise chutes of rectangular It-isusualto regard-theaflownf air:intoia fiame cross-section which are convergent in .thedirection of:airs flOWlBIld this. lends itself to their. :con-

structionlfrom sheet metal. The extent to which air directing means:project into the bore of 'the tube is small and: the nature ofanvsuch-projeo- "tlOIIiSIiSUCh'thBItJ it does not substantiallyinterffere with the air :flo'w within the tube .vso \that serious localturbulence caused thereby is avoided and alsopthe susceptibility oftheimeans to damage by the impin'gement of flame orrhotxlgasis whichIFig. 1 l is a sectional :views showingaiflamettribe and: associatedparts together witht-themethodtof mountingosandi locating.

Fig. :2 is: a .partiy sectioned: illustrationwshowing theexternalrappearance ofzza flame tube.

Fig; '3 iswawsectdonal. fragmentary viewcofzone air directingrmeans.

Fig.4 isa representationiof a :power unitfor; i at propulsion :intended.for *use on aan zaircrait and is an .exampleiofronercasei inawhiohvthe'invention may be applied.

' tends.

Referring first to Fig. 4, a compressor rotor 22 of a double sidedcentrifugal compressor draws in air through double air intakes 23 andthe compressed air is delivered from the compressor casing 24 throughoutlets 25 to a plurality of interconnected combustion chambers or aircasings I arranged symmetrically in a circular series around the axis ofthe compressor 22. Each chamber I comprises a flame tube 8 provided withsuitable apertures through which the air enters and by means of a fuelinjector 4 fuel under pressure from a supply source and pump 26 issprayed into the flame tube 8 and the gaseous mixture ignited, forexample by means of an electric spark plug. The gaseous products arethen delivered through elbow ducts to the nozzle assembly 6 of a turbine3| mounted on the same shaft 32 as the compressor rotor 22. The hotgases thus drive turbine 3| which in turn drives the rotor 22, and thegases after passing through the turbine 3| flow into an annular duct 33formed between a conical fairing 34 and a jet pipe 35, being finallyejected to atmosphere through the outlet 36 of jet pipe 35 and formingin this way a main propulsive jet stream.

The flame tube 8 is illustrated on a larger scale in Fig. 1. Eachcombustion chamber consists of a cylindrical wall I, with an air entry 2and with one end closed by a hemispherical end 3 through which extendsaxially a fuel injector 4 the purpose of which is to inject liquid fuelin at atomised state.' From the interior of the combustion chamber Ithere leads an elbowed receiving duct 5 to lead combustion productslaterally out of the chamber I to the nozzles 6 of the gas turbine 3|(Fig. 4). The lateral air duct 1 leads from the combustion chamber I toan identical neighbouring chamber.

Coaxially within the chamber I is mounted the flame tube. This consistsof a sheet metal body 8 made in the form of a tubular cylinder with anopen end at 9 which fits spigot-wise into the corresponding open end ofthe receiving duct 5, and is a sliding fit therein. The

other end of the flame tube 8 is virtually closed by a dished endclosure II] which has minor perforations through it arranged as a ringat II. The closure II] also has an axial central hole provided with aninwardly extending mounting sleeve, through which the fuel injector 4ex- Out side-the closure III there is also provided a frusto conicalscreen I2 with a comparatively large central aperture. The space betweenthe elements II] and I2 serves as a distributing duct to lead primaryair to the entrance I3 of air directing chutes I4 which are arranged asa ring or circumferential series equally spaced around the flame tubeand terminating in openings in the wall of the flame tube, the directionof the chutes being tangential. The air entering chutes I4 when itreaches the interior or bore of the flame tube 8 constitutes a now ofvortex nature and it will be appreciated that this air mixing with theinjected fuel burns in the region of the closed end of the flame tube;this combustion being relatively rich mixture combustion which isself-sustaining in all intended operational conditions is the primarycombustion. The fact that it is self-sustaining appears to be duelargely to the fact that the vorticity produces a reversal of flow orreversed core whereby a certain amount of flame is always sustained inthe region of fuel injection. Beyond the region of primary combustionopenings are provided in the flame tube wall for the introduction ofsec- '4 ondary air. Some of these simply constitute rings of plain holesI5 but other openings I6 and I1 are associated with air directing chutesISA, HA. The openings I6 are arranged in a ring and it has been foundsuccessful to arrange these with an opposite rotational direction to thechutes I4. The chutes I'IA again arranged as a ring and axially spacedfrom the chutes I 6A are again oppositely handed, that is to say theyare of the same hand as the chutes I4. The last openings in thedownstream direction are somewhat elongated holes I8 this shape havingbeen found most suitable for the introduction of tertiary air in thisregion.

The flame tube of which the open end 9 is supported against all movementexcept axial by its sliding fit, is supported towards its closed end byvarious means which may be used together or alternatively. In some casesit may be supported by and located with respect to the fuel injection 4or any tubular fuel injector mounting such as 4A. Again it may besupported by an igniter plug exemplified at I9 or in the case of acombustion chamber not having such a plug a dummyv plug occupying theplace of an igniter plug, and further it may be supported by a tubularelement 20 which constitutes a branch connection between the interior ofthe flame tube 8 and a like adjacent flame tube in an adjacentcombustion chamber. connection 20 lies within the branch duct I and maybe supported therein by a perforated plate 7 2I interposed in anassembly joint of the duct I.

The general form of the chutes is illustrated by Fig. 3 in which it canbe seen that the air passage of a chute is convergent in the directionof flow and that the structure of the chute lies mainly external to thebore of the flame tube the only internal projection being so inclined tothe direction of whirl of the gases within the flame tube and soadequately cooled by the air flow in the chute that the structure is notsusceptible to damage due to the combustion nor is it such as to promoteany substantial amount of turbulence within the bore. The chutes at I4only differ from the form represented in Fig. 3 by having the airentrance to the chute somewhat differently disposed as can be seen mostclearly at I3 in Fig. 2.

In the construction described it can be seen that the flame tube as awhole can be mounted within the combustion chamber I prior to finalassembly and sufficiently supported therein for the combustion chamberwith flame tube complete to be assembled to the other parts. In generalso far as the flame tube itself is concerned the closed end is regardedas the upstream end and the open end 9 the downstream end.

I claim:

1. In combustion apparatus for the combustion of fuel in a combustionsupporting gas supplied as a high velocity stream, and of the kindcomprising a flame tube which is open at its downstream end for emissionof combustion products and is provided with swirl inlets at its upstreamend constituting main primary combustion supporting gas entries fromsaid stream and with additional inlets downstream of said primaryentries constituting secondary combustion supporting gas entries, incombination with a fuel injector which enters the upstream end of saidflame tube along the axis of the tube, and which accordingly directs thefuel into the core of reverse flow which will be formed by the primarycombustion supporting gas entering by said swirl inlets and swirlingaround the axis of the tube, the improve- As is apparent the branch mentthat said flame tube is made up of a peripheral wall and an upstream endclosure wall and said swirl inlets are ports formed in said peripheralwall, adjacent to said end closure wall and around said fuel injector,and are shaped to direct the air into the flame tube substantiallytangentially on to the inner surface of the said peripheral wall.

2. Combustion apparatus according to claim 1 wherein said inlets forsecondary combustion supporting gas are also located to direct thecombustion supporting gas inward substantially tangentially to theperiphery of said tube.

3. Combustion apparatus according to claim 2 wherein the said inlets forprimary combustion supporting gas are located to direct said primarycombustion supporting gas to swirl around the axis of the tube in onesense and the inlets for secondary combustion supporting gas are locatedto direct said secondary combustion supporting gas to swirl in theopposite sense around the axis of said tube.

4. Combustion apparatus according to claim 3 in which there are inletsdownstream of the inlets for secondary combustion supporting gas, said 6downstream inlets being located to direct additional secondarycombustion supporting gas to swirl in the same sense as the primary air.

MATTHEW LEWIS NATHAN.

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